Fusible Metal Film Resistors Welwyn Components FM Series • Predictable fusing characteristics • Flameproof protection Electrical Data FM1/4 FM1/2 FM1 Power rating at 70˚ C watts 0.25 0.5 1.0 Resistance range ohms 0R1 - 10K 0R1 - 27K 0R2 - 1K5 volts 250 350 350 Limiting element voltage TCR ppm/˚ C Resistance tolerance 250 % 5 Standard values E24 preferred Thermal impedance 150 ˚ C/watt Ambient temperature range 100 120 ˚C -55 to 155 Physical Data Dimensions (mm) & Weight (g) PCB Min. bend radius Wt. nom L max D max f min d nom mounting centres 6.2 2.5 2.3 21.0 0.6 10.2 0.6 0.3 FM1/2 9.0 3.4 19.6 0.8 12.7 1.2 0.6 FM1 12.5 4.2 17.8 0.8 18.4 1.2 0.9 Type FM1/4 d D L f Construction Marking The metal film is deposited on a high purity ceramic rod. End caps are force fitted and termination wires welded to the caps. The resistive film is adjusted to the required value by a special helical cut; finally the cement protection is applied to the resistor body and marked with indelible ink. Resistors are colour coded with five bands. Four of the bands are used to indicate value and tolerance, with IEC 62 colours being used. A fifth yellow band denotes constant voltage fusibility. Solvent Resistance Terminations Material Solder-coated copper wire. Strength The terminations meet the requirements of IEC 68.2.21. Solderability The terminations meet the requirements of IEC 115-1, Clause 4.17.3.2. The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed circuits. Flammability The resistors will not burn or emit incandescent particles under any condition of applied temperature or power overload. General Note Welwyn Components reserves the right to make changes in product specification without notice or liability. All information is subject to Welwyn’s own data and is considered accurate at time of going to print. A subsidiary of TT electronics plc © Welwyn Components Limited · Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: [email protected] · Website: www.welwyn-tt.com 164 Issue C 01.07 B · 03.02 Fusible Metal Film Resistors Welwyn Components FM Series Performance Data Maximum Load: 1000 hours at 70˚C R% 3 Shelf life: 12 months at room temperature R% 2 Derating from rated power at 70˚ C zero at 155˚ C Temperature rapid change R% 0.5 Resistance to solder heat R% 0.5 FM1 Fuse Times Pulse Time (seconds) Pulse Time (seconds) FM1/2 Fuse Times Initial Power (W) Initial Power (W) Packaging FM1/4 Fuse Times The standard taping method and critical dimensions are shown in figure 1. Component wire will not protrude beyond the outside edge of the tapes. Lead Formed resistors can also be supplied. Standard options of Lancet, Radial and Goalpost forming are shown in Lead Form Information section. Pulse Time (seconds) All resistors are supplied tape packed ready for loading on to automatic sequencing and insertion machines. Initial Power (W) A detailed Packaging Data Sheet is available on request. Figure 1 Fusing After fusing the final resistance value will be 50 times the initial value. 5 f1 6 f2 52 Body Location f1 – f2 6 1.4 mm Standard Quantities Per Package Type FM1/4 FM1/2 FM1 Large ammo pack 5000 2500 1500 © Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: [email protected] · Website: www.welwyn-tt.com B · 03.02 Issue C 01.07 165